netdev - Re: [PATCH v23 08/22] cxl/hdm: Add support for getting region from committed decoder

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Message-ID: <03ab7820-a6e0-4655-bae7-61d2d0b7dfd6@amd.com>
Date: Wed, 11 Feb 2026 16:11:55 -0600
From: "Cheatham, Benjamin" <benjamin.cheatham@....com>
To: <alejandro.lucero-palau@....com>
CC: Alejandro Lucero <alucerop@....com>, <linux-cxl@...r.kernel.org>,
	<netdev@...r.kernel.org>, <dan.j.williams@...el.com>, <edward.cree@....com>,
	<davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<edumazet@...gle.com>, <dave.jiang@...el.com>
Subject: Re: [PATCH v23 08/22] cxl/hdm: Add support for getting region from
 committed decoder

On 2/1/2026 9:54 AM, alejandro.lucero-palau@....com wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> A Type2 device configured by the BIOS can already have its HDM
> committed. Add a cxl_get_committed_decoder() function for cheking
> so after memdev creation. A CXL region should have been created
> during memdev initialization, therefore a Type2 driver can ask for
> such a region for working with the HPA. If the HDM is not committed,
> a Type2 driver will create the region after obtaining proper HPA
> and DPA space.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> ---
>  drivers/cxl/core/hdm.c | 39 +++++++++++++++++++++++++++++++++++++++
>  include/cxl/cxl.h      |  3 +++
>  2 files changed, 42 insertions(+)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 6e516c69b2d2..a172ce4e9b19 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -686,6 +686,45 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, u64 size)
>  	return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled);
>  }
>  
> +static int find_committed_endpoint_decoder(struct device *dev, const void *data)
> +{
> +	struct cxl_endpoint_decoder *cxled;
> +	struct cxl_port *port;
> +
> +	if (!is_endpoint_decoder(dev))
> +		return 0;
> +
> +	cxled = to_cxl_endpoint_decoder(dev);
> +	port = cxled_to_port(cxled);
> +
> +	return cxled->cxld.id == port->hdm_end;

Is this the way you're supposed to check if a decoder is committed? The doc comment for @hdm_end in
struct cxl_port says it's just the last allocated decoder. If allocated decoders are always committed then
I'm fine with this, otherwise I think you'd want to a register read or something to find the commit state.
> +}
> +
> +struct cxl_endpoint_decoder *cxl_get_committed_decoder(struct cxl_memdev *cxlmd,
> +						       struct cxl_region **cxlr)
> +{
> +	struct cxl_port *endpoint = cxlmd->endpoint;
> +	struct cxl_endpoint_decoder *cxled;
> +	struct device *cxled_dev;
> +
> +	if (!endpoint)
> +		return NULL;
> +
> +	guard(rwsem_read)(&cxl_rwsem.dpa);
> +	cxled_dev = device_find_child(&endpoint->dev, NULL,
> +				      find_committed_endpoint_decoder);
> +
> +	if (!cxled_dev)
> +		return NULL;
> +
> +	cxled = to_cxl_endpoint_decoder(cxled_dev);
> +	*cxlr = cxled->cxld.region;
> +
> +	put_device(cxled_dev);
> +	return cxled;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_get_committed_decoder, "CXL");
> +
>  static void cxld_set_interleave(struct cxl_decoder *cxld, u32 *ctrl)
>  {
>  	u16 eig;
> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> index 6f8d365067af..928276dba952 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h
> @@ -249,4 +249,7 @@ int cxl_map_component_regs(const struct cxl_register_map *map,
>  int cxl_set_capacity(struct cxl_dev_state *cxlds, u64 capacity);
>  struct cxl_memdev *devm_cxl_add_memdev(struct cxl_dev_state *cxlds,
>  				       const struct cxl_memdev_attach *attach);
> +struct cxl_region;
> +struct cxl_endpoint_decoder *cxl_get_committed_decoder(struct cxl_memdev *cxlmd,
> +						       struct cxl_region **cxlr);
>  #endif /* __CXL_CXL_H__ */